Finger millet or Ragi (Eleusine coracana) is a grain of unique nutritional qualities and technological characteristics. It is an important staple food for people belonging to low income groups in Indian subcontinent and several African countries. Millet is a good source of carbohydrates, sulphur amino acids, dietary fibre, micro-nutrients, phytochemicals and is the richest source of calcium among cereals (J. H. Hulse, E. M. Laing and O. E. Pearson, Sorghum and millets: composition and nutritive value, Academic press, New York, 1980). It is believed that among millet consumers, incidence of diabetes mellitus, cardiovascular a diseases, duodenal ulcer and other gastro-intestinal tract related disorders is relatively less (C. Gopalan Carbohydrates in diabetic diet Bulletin of Nutrition Foundation, India, p3, 1981) and to F. I. Tovey (Duodenal ulcer in Mysore: Characteristics and aetiological factors, Tropical and Geographical Medicine, 24, 107-117, 1972).
Popping of cereals, millet and some of the legumes is one of the important food processing technology followed worldwide (J. L. Malfait, Puffed food starch product and C method for making the same, US Patent Application No. US2002/0071892A1, 2002). On the other hand, puffing or preparation of expanded cereals is largely applied to rice (R. M. Huang, M. C. Chou, C. Y. Lii, Effects of the characteristics of rice and the processing conditions on the expansion ratio of dry cooked rice. Food Science, 25, 383-393,1998) and similar kind of products from other cereals are not generally prepared. Probably the special features of rice endosperm texture containing very low proportion of protein matrix or cell wall proteins compared to other cereals could be the reason for its puffing characteristics. The puffed or expanded rice is superior to popped rice with respect to degree of precooking, crunchiness, fiber regulation, shelf-life and sensory attributes for which reference may be made to G. Murugesan and K. R. Bhattacharya (Rheological and hydration properties of popped rice. Journal of Texture Studies, 20, 325-333, 1990) and R. J. MacGregor, D. M. MacGregor, A. Lueck, [Process for popping wild rice. U.S. Pat. No. 4,876,099, U.S. Ser. No. 07/223,608 (19880725), 1988]. Popping as well as puffing is a high temperature short time treatment (HTST) to grains and generally involves dropping the grains in sand, salt or air heated to about 250° C. and continuous agitation followed by separation of the popped grains from heat transfer media by sieving. Popping is also practiced using edible oil as heat transfer media, contact heat in iron or earthen pan. Both popped and puffed cereals are ready-to-eat products with crunchy texture and desirable aroma, besides, during popping the seed born microflora are destroyed and the protein gets denatured. Popped or puffed cereals could be k used as snacks as such or after seasoning with oil and spice or coating with flavoring and such other agents to improve the sensory attributes and also could be blended with processed legumes, jaggery or sugar to prepare nutritious supplementary foods for weaning children and mothers. Both puffing and popping are dry process, and have economical and technological edge over other kinds of cereal processing technologies for preparation of ready-to-eat foods.
However, drawbacks of popping process for cereals in general, and finger millet in particular, are that, the grains are mixed with sand or salt heated to about 230° C. and the popped material is separated by sieving. Fine sand or salt particles adhere to the popped grains especially in the crease portion of the expanded endosperm. This not only affects their eating qualities but also increase the silica contents. Another drawback of the hitherto known process of the popping of millets is that, the endosperm expands and gets exposed to the hot popping medium and a portion of it very often gets charred, there by reducing its economical value and sensory qualities. Another drawback of the hitherto followed process for popping millet is that, the husk or the seed coat matter of the kernel gets embedded and covered by the expanded floury endosperm and its separation is not possible by known methods. As a result, the cellulosic fiber content of the seed coat matter imparts chewy texture and dark color, and affects the organoleptic qualities and food values of the product. Since, finger millet endosperm is of floury texture attached rigidly with the seed coat, efforts to mill the popped millet to prepare debranned or dehusked grains has not been successful (N. G. Malleshi and H. S. R. Desikachar, Varietal difference in puffing quality of ragi. Journal of Food Science and Technology, 18, 30-32, 1981) and preparation of puffed or expanded millet was not practiced to the best of our knowledge. However, decorticated finger millet which is free from coarse seed coat matter, prepared according to the recently developed process (Malleshi N. G. A process for preparation of decorticated finger millet. Indian Patent Application No. 69/DEL/2002, 2002) has promise for puffing and diversification of puffed or expanded millet as snack, supplementary foods, specialty foods and health foods.